Device for simultaneously cutting the sewing threads in a sewing machine



Jan. 13, 1970 N. MARFORIO 3,

DEVICE FOR SIMULTANEOUSLY CUTTING THE SEWING THREADS IN A SEWING MACHINE Filed July 8, 1968 5 Sheets-Sheet 1 FIG.7

Jan. 13, 1970 MARFORlO 3,489,115

DEVICE FOR SIMULTANEOUSLY CUTTING THE SEWING THREADS IN A SEWING MACHINE Filed July 8, 1968 3 Sheets-Sheet 2 PIIIA Z FIG.6

Jan. 13, 1970 N. MARFORIO 3,489,115

DEVICE FOR SIMULTANEOUSLY CUTTING THE. SEWING THREADS IN A SEWING MACHINE Filed July 8, 1968 3 Sheets-Sheet 3 United States Patent 3,489,115 DEVICE FOR SIMULTANEOUSLY CUTTING THE SEWING THREADS IN A SEWING MACHINE N erino Marforio, Milan, Italy, assignor to S.p.A. Vu'gimo Rimoldi & C., Milan, Italy Filed July 8, 1968, Ser. No. 743,489 Claims priority, application Italy, July 7, 1967, 18,132/ 67 Int. Cl. Db 65/00, 47/00 US. Cl. 112-252 8 Claims ABSTRACT OF THE DISCLOSURE A cutter blade is freely reciprocable along a portion of its stroke in each direction and drives a counterblade and clamp along the remainder of its stroke in each direction.

This invention relates to a thread cutting device for cutting simultaneously the sewing threads in a sewing machine, said device comprising a shiftable cutter, a counterblade and a clamp for gripping the cut threads.

Thread cutting devices provided with counterblade and clamp for gripping the cut threads are known, but in all those devices the most serious inconvenience was determined by the too large distance between the area where the sewing threads are caught by the cutter and the counterblade being formed by a stationary element arranged on the machine frame.

On the other hand, the blade could not be provided near the gripping area, as other important devices of the machine were provided there, such as, i.e., the looper, the feeding device and the needle during its alternatively working movements said devices because of their struc ture occupying space useful for the provision of the counterblade and of the thread-gripping clamp.

For that reason, the cutter should be provided so as to be able to catch the threads from the stitch-forming area and to carry them against the counterblade and in the clamp.

This often produces thread breakages, mainly due to the fact that the threads were caught by the cutter blade and carried against said counterblade, so that a slight increasing of thread tension was sufficient for the threads to be cut by the blade before being gripped by the clamp.

The aim of this invention is to avoid the above mentioned inconvenience, by providing a thread cutting device, which is able to cut the sewin-g threads after the latter have been gripped by the clamp. For reaching this aim, the technical problem to be solved was to provide improved thread putting device in order to secure the cut of the threads after they are gripped by the clamp and whereby it can be possible to restart the sewing opreation avoiding skipstitching due to thread shortage or unthreading in the machine. For solving this technical problem a thread cutting device as above mentioned has been realized, wherein the cutter, being moved by pneumatic means from a resting to a cutting position and vice versa, is connected with the counterblade and with the clamp to bring them after a short free running, near to the threads to be gripped and cut; and wherein thread pulling devices are provided, which are connected with each other and with the cutter, and which are caused to pull thread from the bobbins in order to avoid breakages of the sewing threads.

The objects and the advantages of this invention will become apparent from the description now to follow of a preferred embodiment thereof shown by way of example in the accompanying drawings, in which:

FIGURE 1 shows a sewing machine provided with thread cutting device;

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FIGURE 2 is an enlarged section view of the cutter and its driving means;

FIGURES 3 and 4 are two different positions of the cutter in respect of the counterblade and the clamp;

FIGURES 5 and 6 are front positions of the sewing threads before and after being cut by the cutter;

FIGURE 7 is a section view of the machine along the line VII-VII of FIGURE 1;

FIGURES 8 and 9 are two enlarged section views of the machine respectively along the lines VIII-VIII and IXIX of FIGURE 7.

FIGURE 1 shows schematically a chain stitch sewing machine in which the frame 1 comprises a base 2, a standard 3, an arm 4 integral with said standard, and a head 5 provided on the free top of the arm 4. Within the base 2 there are the known feeding means and the stitch length adjusting means and a hook '6 which cooperates with one or more needles 7 for the stitching operation.

The needle 7 is fixed by a suitable clam-p 8 to the usual needle bar 9 which is sliding mounted within the head 5 and is moved by usual driving means being provided within the arm 4 and not shown in the drawings. On the front side of the standard 3 a tension carrying plate 10 is provided, which tensions 11, 12 and 13 are mounted on. A sliding plate 14 is interposed between the plate 10 and said tensions, the operation of which will be explained later.

The tensions 11 and 12 are provided to friction the needle thread in a proper way and the tension 13 is provided to friction the hook thread in a proper way.

When on the machine one needle 7 only is mounted, the tension 12 is not used.

The above described sewing machine is provided with a thread cutting device 15 for cutting simultaneously the sewing thread, which device is the object of this invention.

Said thread cutting device 15 (see FIGS. 2 to 4) is mounted on the base 2 under a needle plate 16 and is placed in front of the hook 6. Said device comprises a shiftable cutter 17 interposed between two plates which are respectively a counterblade 18 for said cutter and a clamp 19 for gripping the cut threads.

The cutter 17, which is usually in a resting position out of the working area of the hook 6 and of the needle 7, is moved towards and from the cutting position by pneumatic means that are a plunger 20 mounted within a cylinder 21 and pushed first in one and then in the opposite direction by a pneumatic flow, flowing alternatively within the cylinder 21 and through conduits 22 and 23 which are connected with said cylinder in such a way as to result one at one part and the other one at the other part of the plunger 20. Said conduits are suitably connected to each other by a suitable pneumatic plunger valve, not shown in the drawings.

By operating a suitable driving means, such as a treadle, the pneumatic valve supplies compressed air to the cylinder 21, at first through the conduit 22, in such a way as to move the plunger 20 towards the right, and with it to have the cutter 17 shifted into the cutting position, which is illustrated by dotted lines in FIG. 2. Afterwards, the pneumatic valve supplies compressed air to the cylinder 21 through the conduit 23, discharging the air contained in the cylinder through the conduit 22, so that the plunger 20 is brought back towards the left and the cutter 17 in the resting position. The cutter 17, during the movement to the cutting position, runs freely for a short period and after that brings both the counter-blade 18 and the clamp 19 as near as possible to the sewing threads to be gripped and cut.

During the return movement towards the resting position, the cutter first runs freely backwards bringing the gripped threads towards the counterblade 18 and the clamp 19, which remain in the previously reached position, in order to grip and cut the threads before beginning the movement with the cutter towards said resting position.

For attaining the sequence of movements according to the above mentioned order, the counterblade 18 and the clamp 19 have been provided with an elongated slot 24 being as long as the free run of the cutter 17, which is provided with a pin 25 disposed throughout said cutter and having each outer end engaged in a slidable way within said slot 24, At first, when the cutter 17 is in the resting position, the pin 25 is placed within said slots 24, placed completely to the left, having the free part of them placed at right (FIG. 3) so that the bringing of said counterblade 18 and clamp 19 can be effected only after the pin 25 has run for the entire length of the slots.

Thus the cutter moves by itself until the pin has reached the opposite wall of said slots. From this moment until the reaching of the cutting position, the movement of the cutter 17 continues together with said counterblade and clamp.

The free run of the cutter is necessary for disconnecting a blade 26 with which the cutter 17 is provided at its free end 27, from the counterblade 18 and the clamp 19 for gripping the sewing threads. Vice versa the free returning run towards the resting position is necessary for bringing up the previously caught threads on the clamp for gripping them and against the counterblade for cutting them. In fact this is possible as the pin 25 is placed completely to the right, having the free part of the slots 24 placed at left (FIG. 4) so that the bringing up of said counterblade and clamp can be effected only after said pin has run for the entire length of the slots and consequently the blade 26 is already reinserted in the counterblade 18 and in the clamp 19.

For avoiding that the counterblade 18 and the clamp 19 move before the cutter has made its entire free run, they are provided with two notches 28 and 29 within which a protrusion 30 of a leaf spring 31 is engaged and works as known. Said spring is used for contrasting the movements of saidcounterblade and clamp until the pin 25 has been brought up by the cutter 17, and has run for the entire length of the slots 24 and has reached against the opposite wall of them. The same performance repeats also during the return run of the cutter. In fact, the protrusion 30, on leaving a notch under the pushing given by the pin to the blade, inserts in the other notch, as this one is near said protrusion, the notches being placed at a distance from each other which is as long as the distance still remaining to be run by the cutter 17 for reaching its own cutting position. The cutter 17 has a recess 32 which extends substantialy for the same length as the notches 28 and 29, and which is provided to prevent the cutter interfering with said leaf spring.

When the cutter 17 is shifted towards the cutting position, the free end 27 contacts a portion 33 of the needle thread 34 and a portion 35 of the hook thread (FIGS. and 6) and causes a lateral displacement of them in the recess being provided in the front of the blade 26,

As the thread portions are running between the hook 6 and the work 36 while said hook is in its own position more laterally displaced from the vertical path travelled by the needle 7 which stops at its own top dead point while the work-feeding means too (not shown) have completely displaced as far forward as necessary, the lateral displacement of the threads being caused by the end 27 of the cutter, could stretch them excessively and break them before they are gripped by the clamp 19.

Besides, the breakage of the threads could happen at any point, also near the needle eye or the eye of the hook, with consequent unthreading when restarting the sewing.

For avoiding this inconvenience and for having the cut of the threads always in the same precise place of the portions 33 and 35 and, particularly, for having the hook thread gripped by the clamp 19 and the thread 34 with a convenient length for forming the new stitch, the sewing machine has been provided with a thread pulling device 37 disposed across the path of the needle thread and with a device 38 disposed across the path of the hook thread. The devices 37 and 38, the first being supported by the arm 4 and the other by the base 2 of the frame 1, are provided for pulling thread from the bobbins before the thread cutting device 15 starts to function; said thread pulling devices being connected with the thread cutting device by means of the hand control of the above mentioned pneumatic valve. In fact, said control is connected by a chain 39 with a lever 40 keyed on a shaft 41 mounted rotating on the standard 3 of the frame 1. Said shaft 41 (see also FIG. 8) is provided to transmit the movements of the lever 40 to the sliding plate 14 and at the same time to a longitudinal shaft 42 mounted rotating within the arm 4.

On the free end of the shaft 41 is mounted an arm 43 provided with a pin 44 which has its free end engaged within a slot of the sliding plate 14. The rotations of the shaft 41, being caused ,by the lever 40, are transmitted to the arm 43, which, by said pin, slides the plate 14 in respect of the tensions 11, 12 and 13 and by means of bosses 45 which said plate is provided with, the discs of said tensions are moved away each from the other; releasing the threads from the frictioning to which they are subjected.

At the same time, an arm 46 provided on the shaft 41 transmits said rotations to another arm 47 keyed on the shaft 42 by means of a rod 48.

The rotations of the shaft 42 are effected in opposition to the action of a coil spring 49 having one end 50 fixed to the frame 1 and the other end 52 fixed to a ring 53 fixed to said shaftl42.

Because of the action of said coil spring 49, when the movements of the lever 40 stops, the shaft 42 is brought again in a predetermined resting position.

The shaft 42 has an articulated arm 54 hinged to an articulated lever 55 substantially disposed at and keyed on a shaft 56 which supports a thread pulling device 57.

As it can be seen from that, the thread pulling device moves from its usual position as soon as the shaft 42 is oscillated by the lever 40, on pulling threads from the bobbins and not from the needle 7, as the tensions 11, 12 and 13 have meanwhile been opened.

The hook thread pulling is made in similar way by the thread pulling device 38, being directly connected with the shaft 42 by a normal wire 58 contained sliding within a suitable sheath 59.

On the shaft 42 another arm 60 is provided, which is connected at its free end with one end of the wire 58, the other end of which is fixed to an end 61 of a bell crank 62 of the thread pulling device.

Said bell crank 62 is fulcrummed in the middle on a pivot pin 63 of the base 2, and has its own other free end 64 connected with a sliding rod 65 provided with a thread guide 66.

At every rotation of the shaft 42, the bell crank 62 oscillates about its own pivot pin in opposition to the action of check coil spring 67 pulling the thread guide 66 away from the two fixed thread guides 68 and 69 and therefore, pulling threads from the bobbins. The thread pulling device 57 is provided with a thread guide being placed between two fixed guides 71 and 72.

The fixed thread guides are provided to avoid the threads curling or being incorrectly disposed. As the pneumatic valve driving means is operated by the operative, by means of the chain 39, the lever 40 is rotated and caused, as previously explained, the pulling of threads from the bobbins and only by continuing the operation on said means the pneumative valve causes the thread cutting device 15 to go into action. The sewing machine is usually provided with a hand operated driving means which works independently and is not shown in the drawings, and

which is connected with tie known presser device, to allow the removal of the work from the sewing machine and connected with the motor being provided with means for the change of the needle position from the lower to the upper position.

Providing a driving means being connected with the presser foot when the needle is in the upper position for to be able to lift the presser foot when the needle is in the lower position for changing stitching path, and to lift the presser foot when the needle is in the upper position for removing the finished work, on ending of the so-called blind seams and namely the seams not going out of the edges of the work, i.e. as occurs on sewing pockets.

What is claimed is:

1. A sewing machine comprising a thread cutting device for simultaneously cutting the needle and hook threads, said device comprising a reciprocable cutter blade, a counterblade, and a clamp for gripping the cut threads, a drive means for reciprocating said cutter blade between a resting and cutting position, said cutter blade being freely reciprocable along a portion of its stroke in each of its reciprocal directions relative to said counterblade and clamp, said cutter blade driving said counterblade and clamp along the remainder of its stroke in each of said directions, a thread pulling device associated with each of the bobbins for the needle thread and the hook thread, respectively, said pulling devices being drivingly interrelated with the cutter blade and being arranged to pull thread from the respective bobbins and pursuant to said cutter blade effecting a cutting stroke on said thread whereby breakage of the thread is avoided excepting as effected by said cutter blade.

21 The sewing machine of claim 1, wherein said cutter blade in moving from said resting to said cutting position travels freely of said counterblade and clamp during the beginning of its stroke and during the latter part thereof drives said counterblade and clamp towards said cutting position, and said cutter blade in moving along the return stroke from said cutting to said resting position travels freely of said counterblade and clamp during the beginning of its stroke and during the latter part thereof drives said counterblade and clamp towards said rest position.

3. The sewing machine of claim 1, said cutter blade being positioned parallel to and between said counterblade and said clamp, a closed ended slot in said counterblade and in said clamp elongated in the direction of reciprocation of said cutter blade, a pin on said cutter blade extending into each of said slots and being slidable along the longitudinal extent thereof, said slots being oppositely facing each other and being as long as the free travel of said cutter blade relative to said counterblade and clamp.

4. The sewing machine of claim 2, said counterblade and said clamp each including two notches spaced apart from each other along a surface extent thereof, the distance between notches being equal to the length of the stroke portion along which said cutter blade drives said counterblade and said clamp, a resiliently urged detent member engageable in said notches for yieldingly holding said counterblade and said clamp against movement excepting when being driven by said cutter blade during said latter part of the cutter blade stroke.

5. The sewing machine of claim 1, said drive means being a bi-directional pneumatic drive means including a pneumatic valve for determining the direction in which said drive means operates, a hand operated control means for actuating said valve, said control means being drivingly associated with said thread pulling devices whereby actuation of said pneumatic valve to cause said drive means to drive said cutter blade correspondingly drives said thread pulling devices.

6. The sewing machine of claim 1, wherein a first of said thread pulling devices comprises a rotary shaft, an articulated arm on said shaft hingedly connected with an articulated lever which is rotatively connected with a first thread pulling lever, a second of said thread pulling devices comprising a symmetrically fulcrummed bell crank having one free end connected with a second thread pulling member, another free end of said bell crank being connected to a flexible wire means which is also connected with a radially projecting arm on said shaft, the rotational movement of said shaft being transmitted through said wire means to said second thread pulling member.

7. The sewing machine of claim 6, including a personactuable control means for actuating said drive means, said control means being arranged to effect turning of said shaft concurrently as it actuates said drive means pursuant to actuation of said control means by a person.

8. The sewing machine of claim 7, including tension members for tensioning the needle and hook threads in the region between the needle and hook, respectively, and the respective thread bobbins, said control means being arranged to release said tension members from their tensioning position concurrently with actuation of said drive means.

References Cited UNITED STATES PATENTS 2,707,927 5/1955 Artzt et al 112-252 3,386,402 6/1968 Ross 112-252 3,424,117 1/1969 Schopf 1l2-252 JAMES R. BOLER, Primary Examiner US. Cl. X.R. 112254 

